It depends on what you are actually wanting to do.

encodeURI assumes that the input is a complete URI that might have some characters which need encoding in it.

encodeURIComponent will encode everything with special meaning, so you use it for components of URIs such as:

const world = 'A string with symbols & characters that have special meaning?'
const uri = 'http://example.com/foo?hello=' + encodeURIComponent(world)

For the visually minded, here's a table showing the effects of encodeURI(), encodeURIComponent() and escape() on the commonly-used symbolic ASCII characters:

Char  encUrI  encURIComp  escape
*     *       *           *
.     .       .           .
_     _       _           _
-     -       -           -
~     ~       ~           %7E
'     '       '           %27
!     !       !           %21
(     (       (           %28
)     )       )           %29
/     /       %2F         /
+     +       %2B         +
@     @       %40         @
?     ?       %3F         %3F
=     =       %3D         %3D
:     :       %3A         %3A
#     #       %23         %23
;     ;       %3B         %3B
,     ,       %2C         %2C
$     $       %24         %24
&     &       %26         %26
      %20     %20         %20
%     %25     %25         %25
^     %5E     %5E         %5E
[     %5B     %5B         %5B
]     %5D     %5D         %5D
{     %7B     %7B         %7B
}     %7D     %7D         %7D
<     %3C     %3C         %3C
>     %3E     %3E         %3E
"     %22     %22         %22
\     %5C     %5C         %5C
|     %7C     %7C         %7C
`     %60     %60         %60

Another vital difference is that unescape() does not handle multi-byte UTF-8 sequences whereas decodeURIComponent does:

decodeURIComponent("%C3%A9") == "é"
unescape("%C3%A9") == "é"